1. Field of the Invention
The present invention relates, in general, to a method of performing connection admission control in a differentiated services network and, more particularly, to a method of performing adaptive connection admission control in consideration of the states of input calls in the differentiated services network, which, when an ingress edge node exhausts bandwidth allocated thereto, allows the ingress edge node to predict the amount of additional bandwidth required in consideration of the states of calls input to a corresponding path, to request the amount of additional bandwidth from a bandwidth broker, and to perform connection admission control using the bandwidth additionally allocated to the corresponding path in the differentiated services network.
2. Description of the Prior Art
Recently, the Internet is trending toward wide bandwidth due to the development of transmission technology, such as xDSL (Digital Subscriber Line) and Metro Ethernet. Further, with the development of various Internet multimedia contents, new application services requiring Quality of Service (QoS) guarantee, such as Internet broadcasting, Voice over Internet Protocol (VoIP) and Virtual Private Network (VPN), have appeared. Therefore, Internet service users require differentiated services so as to be provided with high quality guaranteed services. Accordingly, technology related to QoS guarantee in the Internet has been introduced as an important research subject. As a result, the QoS guaranteeing technology capable of not only ensuring bandwidth but also satisfying transmission reliability, real-time service, etc. should be proposed so as to deviate from best effort services and support service applications having various requirements in the Internet.
For the QoS guaranteeing technology in the Internet, various functions, such as connection admission control, congestion control, traffic shaping, metering, marking and scheduling, have been proposed. Of the functions, the connection admission control has been primarily required. The object of the connection admission control is to allocate network resources so that a network provides reliable paths capable of guaranteeing a packet loss probability or delay requirement requested by a user.
Of connection admission control schemes, parameter-based admission control mainly used in a telephone network or packet network is disadvantageous in that, since all nodes on a path must manage the parameters and states of connections required to be established by respective ingress edge nodes in the network, serious problems may occur in terms of scalability or complexity in Internet core networks becoming large-sized if the parameter-based admission control scheme is applied to the Internet. Further, measurement-based admission control is problematic in that input traffic should be predicted on the basis of the steady-state average arrival rate at the time of traffic prediction, but there is a high probability that inaccurate connection admission control may be performed.
Further, a static provisioning scheme using a bandwidth broker is disadvantageous in that it is impossible to adapt to network conditions, such as dynamically varying Internet traffic or routing, and the change of the allocation of network resources is performed in certain periods, so that the network resources cannot be efficiently used, and the variously changing states of the network cannot be taken into consideration, thus decreasing the efficiency of resource utilization. A dynamic provisioning scheme being researched to solve the disadvantages is advantageous in that it can dynamically take the states of the network into consideration. However, it is disadvantageous in that a bandwidth broker should be informed of even link-level bandwidths within the network from all nodes and manage the bandwidths, and communications between the respective nodes and the bandwidth broker are frequently performed, so that scalability cannot be provided and then complexity is increased.
Further, a connection admission control scheme using a bandwidth broker is problematic in that the bandwidth broker must perform connection admission control on all connection requests, so that responses to the connection admission are not immediately made and the load of connection admission control is concentrated on the bandwidth broker.
In the meantime, a connection admission control scheme for guaranteeing QoS in the Internet is disclosed in PCT Application No. WO 00/30295 entitled “Providing admission control and network quality of service with a distributed bandwidth broker”. In the scheme of the above patent, respective nodes within a network perform connection admission control using a control message so as to avoid the complexity of the bandwidth broker. Further, a method of initially allocating bandwidth to each path in quotas to perform connection admission control, examining whether quotas can be allocated to all links on the path when the allocated quota is exhausted, and then allocating new quotas to perform connection admission control is disclosed in a reference thesis entitled “On scalable design of bandwidth broker” by Zhi-Li Zhang in IEICE Trans. Commun., Vol. E84-B, No. 8, pp.2011 - 2025, 2001. 8. However, the conventional method disclosed in the thesis is disadvantageous in that the size of a quota must be determined and the bandwidths of all links on the path must be examined so as to allocate new quotas when the quota allocated to the path is exhausted.